Affinity chromatography is chromatography using a column filled with a ligand-immobilized support obtained by immobilizing a substance that specifically binds to a substance for separation and purification (ligand), on an insoluble support. Affinity chromatography is used for, for example, separation and purification of biological substances such as proteins and nucleic acids (JP-A-H06-281638).
As the support for affinity chromatography, for example, particles obtained by crosslinking sugar chains (representatively agarose gel), or particles containing a synthetic polymer as a main component, are used.
Now, for use in bioseparation, a support is usually used repeatedly. However, since there would be residual trace amounts of contaminants in the support even after purification operation, washing step of removing the contaminants to restore the support to the original state is carried out while the support is repeatedly used. In the washing step, usually an operation known as cleaning in place (CIP) is carried out, and a reagent capable of eluting contaminants from the support (CIP agent) is used. Examples of such reagents include alkaline liquids such as sodium hydroxide. In the case of using sodium hydroxide, contaminants such as microorganisms, proteins, lipids and nucleic acids can be effectively removed.
However, when contaminants are removed from the support by using an alkaline liquid, the support is exposed to an alkaline condition. For a support for affinity chromatography using a protein as a ligand, such an alkaline condition is severe and may cause a decrease of capacity due to decreased stability of the ligand. Particularly, most of the supports for affinity chromatography in which the ligand is a polypeptide such as protein A are unstable under the severe alkaline condition.